<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>作业</title>
        <style>
            .main{
                background-color: gray;
            }
        </style>
    </head>
    <body>
        <div class="main">
            <div></div>
            <div class="f1">

                <div class="left">

                </div>

                <div class="right">
<!--                    <div class=""></div>-->
                </div>
            </div>

            <div class="f2"></div>
        </div>
    </body>
</html>